The present invention relates generally to a method and apparatus for dissipating heat from one or more hot components mounted on a printed circuit board, and more particularly to a printed circuit board assembly and method of manufacturing same.
The satisfactory dissipation of thermal energy in hot components used on printed circuit boards has long been a difficult issue to solve. This is particularly true for the thermal energy associated with hot components used on printed circuit boards in small portable devices. Attempts to solve this problem have centered around providing an efficient heat path from the hot component to the outside of the device.
One proposed solution for providing satisfactory dissipation of thermal energy includes mounting a hot component on a metal structure such that it is in communication with an outside housing or a heat sink. One problem with this proposed approach stems from the fact that the assemblies of these hot components that are typically used have tolerances that make it difficult to guarantee good contact between the hot component and the structure. If the structure is too high, pressure can be applied to the component, which can stress the solder joints and cause electrical facture. If, on the other hand, the structure is too low, good thermal contact between the component and the structure is not typically present and thus the component can get too hot.
In these prior configurations, thermal grease or some other compliant member has been typically used to take up the tolerances between the structure and the hot component. However, thermal grease is not designed to be a filler material, but is instead designed to overcome contact resistance encountered when there is good contact force between adjacent materials. Moreover, the use of thermal grease is not a method that is preferred during the manufacturing process, and does not work well if the unit requires disassembly and reassembly. Thus, it has been determined that thermal grease is unacceptable for this purpose.
Further, other compliant members are not as conductive as thermal grease and can be difficult to assemble. Additionally, these other compliant members can put unwanted force on the hot component since they must be compressed to ensure contact, and they still introduce significant thermal resistance. Therefore, these other compliant members are unacceptable as well.
A reliable method for ensuring excellent contact between a hot component and a copper slug, which does not stress the solder joints of the components is therefore highly desirable.
It is therefore an advantage of the present invention to provide a printed circuit board assembly that ensures satisfactory dissipation of heat from any hot components disposed thereon.
It is a further advantage of the present invention to provide a printed circuit board assembly and method of manufacturing same that provides satisfactory dissipation of heat from a hot component, but does not put unwanted stress on the solder joints of the component.
In accordance with the above and other advantages of the present invention a method of attaching a hot component to a printed circuit board is provided. The printed circuit board has at least one opening formed in and extending between a first surface and a second surface. A copper slug is positioned in the opening from the first side of the circuit board and secured thereto. A hot component is positioned on the other side of the circuit board such that its underside lies over the opening. The hot component is then soldered to the circuit board such that a continuous joint is formed between the copper slug and the hot component.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.